Cluster headache is a primary neurovascular disorder, which is characterized by sever unilateral headache. Doctors, scientists and patients have described the pain from cluster headache as the most intense pain a human can endure, worse than child birth or a broken bone.
Cluster headache has been described since the seventeenth century, when it was reported the cyclical, unilaterally and daily pattern of the headache, but Kunkle and his colleagues were the ones who mentioned the particular character of the disease: clusters of attacks that succeed in a very dense temporal sequence and then disappear. For a period of time, it was considered that the disease belongs to the class of vascular migraines, but the International Headache Society (IHS) reclassified cluster headache as a single entity, different from migraine.
Cluster headache prevalence is much lower than other forms of headache, being estimated 0.4% in men and 0.08% in women. The disease is more common in men, with a male-to-female ratio of 3:1.
Cluster Headache Symptoms
The International Headache Society (IHS) classifies cluster headache according to duration in episodic and in chronic form. Episodic cluster headache occurs in periods lasting from 7 days to 1 year; cluster attacks are separated by pain-free intervals lasting at least 2 weeks. In the chronic form of the disease, headaches attacks are recurrent and occur continuously for periods of time longer than one year, with short remission, less than 14 days or with no remission.
The disease affects mostly males and the average age of onset is between 27 and 31 years. Recent studies suggest that in cluster headache pathogenesis, genetic factors are involved.
Cluster term refers to the disease pattern characterized by an agglomeration of attacks that occur in a dense succession of time and then suddenly disappear for varying periods of time.
Average frequency of painful attacks is 1 to 3 per day, but the number of attacks may increase to 15. An active disease cycle may last between 4 and 8 weeks, but it varies from patient to patient.
Painful access suddenly starts and have a duration between 10 and 45 minutes, but most often lasts between 1 and 2 hours. Attacks are triggered during patient’s relaxation periods, but painful crisis typical start within 90 minutes of sleep, and each time occur with the same regularity in the same period of sleep, usually in REM (rapid eye movement) period. During crises, alcohol consumption, vasodilators and histamine administered subcutaneously aggravate cluster headache attacks.
The pain is severe, constant, tenacious and is described as excruciating, stabbing, sharp and lancinating. In most cases, the pain is limited to a localized area around one eye or periorbital, retroorbital, or in temporal region, accompanied by a state of agitation in which the patients do not like to lie down to rest; instead, they are restless and prefer to pace or move around. Sometimes the pain may radiate to lower half of the face, cheek, jaw, occipital, and nuchal regions. Painful attacks are accompanied by autonomic phenomena like unilateral lacrimation, rhinorrhea or nasal obstruction, nasal congestion, conjunctival congestion, and rarely flush, nausea and vomiting. In a number of cases have been reported unilateral ptosis and miosis (small and red eye). Vegetative phenomena may occur before pain and scalp and facial skin are hyperalgal in most cases. In the episodic form of the disease attacks only occur during the activation crisis, which was observed to occur cyclically, in the same month of the year.
Cluster Headache Treatment
Treatment in cluster headache aims a rapid control of acute attacks and prophylaxis to suppress attacks. Pain during the attack reaches a very high intensity, so oral agents are too slow to be effective. The most effective route of administration is either inhaled or intravenous one.
During active period of cluster headache patients should avoid certain substances such as alcohol or inhaling paint or oil-based solvents and exposure to altitude. Sleep attacks can be prevented by administrating 1 mg of ergotamine tartrate with one hour before badtime.
Verapamil is considered the drug of choice for pain prophylaxis and the most notable side effect is constipation. Lithium carbonate administered 2 or 3 times per day is effective in 70% -80% of cases and present as side effects gastrointestinal disturbances, tremor, confusion and weight loss.
The association between verapamil, lithium carbonate and ergotamine administered with one hour before bedtime increase the efficacy of prophylactic treatment.
Cluster attacks are aborted with sumatriptan (an agonist of 5-hydroxitriptamina). In Ekbom’s trials, in 49% of patients attacks were aborted in 10 minutes and in 75% of patients within 15 minutes after administration of sumatriptan.
Ergotamine was widely used before the introduction of sumatriptan into cluster headache therapy. Ergotamine has a fast action administrated sublingual or inhaled. Intramuscular administration produces vomiting, although it has a fast action. The drug of choice remains dihydroergotamine, administered once or twice daily intramuscular or subcutaneous. Is as effective as sumatriptan, but may cause vomiting.
Other therapeutic options are represented by cocaine hydrochloride 5% administered intranasally, or 4% lidocaine solution, acting specifically on sfenopalatine ganglion. The disadvantages of cocaine hydrochloride administration are addiction and tachycardia.
Oxygen inhalation is considered the most effective method in aborting cluster headache crisis, 70% of attacks being aborted in 10 minutes and 90% within 20 minutes.
In the chronic form of cluster headache, without remissions, are used for prophylaxis ergotamine and methysergid. Methysergid is mainly used in cluster headache with attacks that are lasting less than three months.
Cases of cluster headache which are refractory to medical treatment may be treated surgical. Surgical procedures such as invasive nerve blocks and ablative neurosurgical procedures (percutaneous radiofrequency, trigeminal gangliorhizolysis, rhizotomy) all have been implemented successfully. Percutaneous radiofrequency ablation was effective in 50% of patients and failed in about 30% of cases. Side effects include facial dysesthesia, corneal sensory loss, and anesthesia dolorosa.
Gamma-knife radiosurgery represents a less invasive procedure for cluster headache but is associated with an increased risk for facial sensory disturbances.
Deep brain stimulation with implantation of stimulating electrodes under stereotactic guidance into the ipsilateral posterior inferior hypothalamus is also a potential option for refractory cluster headache. Is an invasive procedure and is associated with significant risk of complications such as intracranial hemorrhage, subcutaneous infection, micturition syncope, and transient loss of consciousness.